The book "Investigation of Communist Activities in Seattle, Washington. Hearings, Part 3" by the Committee on Un-American Activities of the United States House of Representatives is a documentary report that reflects key aspects of the investigation of communist activities in and around Seattle. This book is the third part of a series of hearings covering the circumstances and findings of the investigation. In their report, the authors analyze in detail the influence of communist ideologies on the socio-political situation of the region, reveal the peculiarities of the activities of underground organizations and individuals participating in these processes. Readers are provided with unique information and documentary evidence, contributing to a better understanding of the dangers of communist influence and the importance of preventing the spread of anti-American ideas.